XMLHttpRequest fixes

[youennf]

Added some missing testharnessreport.js.
Fixed tests that may timeout (hopefully without changing the behavior of the tests)

[hoppipolla-critic-bot]

Critic review: https://critic.hoppipolla.co.uk/r/623

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In order to help critic track your changes, please do not make in-place history rewrites (e.g. via git rebase -i or git commit --amend) when updating this pull request.

[sideshowbarker]

@youennf there are review comments waiting for your responses over at https://critic.hoppipolla.co.uk/r/623

For example, https://critic.hoppipolla.co.uk/showcomment?chain=1573

[sideshowbarker]

Closing this per comment from @youennf over at https://critic.hoppipolla.co.uk/showcomment?chain=5597

"After a quick check, most of the proposed changes are already integrated into the w3c repo. This request should probably be closed. I will make another one for the remaining bits if needed."